Adaptations to Exercise for a Recreational Triathlete

Continuous aerobic training can improve the effectiveness and efficiency of motor unit firing. They do this through something known as ‘motor learning’. Resistance training is also a way to encourage stimulation of the motor unit, so it is suggested to include resistance training into a triathletes training schedule.

Every time the motor units send the stimulus from nerve to muscle they get better at it. Messages don’t get sent to the wrong muscles en route and messages also get to their target muscles with increasing speed and less delay. A weak message to the motor unit will stimulate the strongest slow twitch fibres. But strong messages will recruit more muscle fibres within the motor unit and stimulate the fast twitch fibres. The fast twitch fibres are the fibres responsible for power and force. Ultimately the goal is to train, through aerobic and resistance training, so as to encourage and teach several neuromuscular motor units to fire simultaneously. Strong, fast athletes have the capability to recruit multiple motor units at once, this means more fibres in use which in turn produces more force. Ben Greenfield states ‘You can have a relatively small number of motor units, but with proper training, gain the ability to recruit a significant number of motor units simultaneously. If this is the case, you don’t need much muscle, just the ability to be able to wholly recruit the muscles that you do have’. With regard to a triathlete training, the aim of weight training is to recruit muscle fibres rather than build muscle. It will also help with injury prevention by encouraging strength around the main joints of the shoulder, knees and hip.

Our body is able to manufacture mitochondria in relation to energy requirements. This enables extra ATP production within the cell to allow for longer periods of muscular contraction. This cycle begins when calcium ions are released by the sarcoplamic reticulum, these ions then start a process with troponin and tropomyosin to allow for the cross- bridge binding of myosin heads to actin. The myofilaments require ATP to release the myosin heads from actin.

There are 3 main types of muscle fibres, slow twitch and fast twitch – type I and II. These fibres increase slightly in diameter as a result of continued aerobic and anaerobic exercise.

Cardiovascular Adaptations

Sustained aerobic exercise increases the oxygen demand of the muscles, and whether the demand is met depends primarily on the adequacy of cardiac output. After several weeks of training the beginner triathlete will increase cardiac output which increases the rate of oxygen delivery to the neuromuscular motor units in the muscle fibres. The athletes heart muscle will increase in weight, volume and chamber size. A mild cardiac hypertrophy is a common adaptation from aerobic exercise, it is shown by an increase in size of the left ventricle and a sight thickening of its walls. The left vetricle sends blood through the aorta to the bodies tissues, so will always be stronger than other heart chambers without exercise. This increase in thickness is the heart muscle cells increasing in size to account for the extra blood volume required by the body during exercise - stroke volume. The main function of the increased stroke volume is to maintain oxygen delivery to the muscle fibres and remove carbon dioxide via the respiratory system.

The athlete will also notice a decrease in maximum heart rate. If your heart rate is too fast the period of ventricular filling is reduced and your stoke volume might be compromised. So the heart expends less energy by contracting less often but more forcibly than it would by contracting more often. With the increased volume, the myocardial fibres become more stretched than at rest, resulting in a more forceful contraction and an increase in force which produces greater chamber emptying. Beachle and Earle state in Essentials of Strength Training and Conditioning that ‘In the progression from rest to steady-state aerobic exercise, cardiac output initially increases rapidly, then more gradually, and subsequently reaches a plateau. Stroke volume begins to increase at the onset of exercise and continues to rise until the individual’s oxygen consumption is at approximately 50% to 60% of maximal oxygen uptake.’

Additional benefits to be gained from physical conditioning are an increase in high-density lipoprotein (HDL). HDL counteracts LDL and helps to prevent the build up of cholesterol or fatty deposits within the coronary arteries and also helps reduce blood clots from low blood viscosity.

Respiratory Adaptations

The respiratory system works in conjunction with the cardiovascular system to provide oxygen and remove water and carbon dioxide. When we exercise the body needs more energy so we begin to breathe faster. Our respiration system generally does not limit aerobic exercise, it is the ability to get the oxygen laden blood to the muscle cells that limits us. The amount we breathe during exercise is indicative of the energy requirements of our muscles. Increased breathing volumes go together with improvements in VO2max as a result of a rise in both tidal volume and breathing frequency. The aerobic triathlete’s training produces significant increases in the amount of oxygen extracted from the circulating blood during activity. So the main adaptation in the respiratory system is an increased tidal volume ( the amount of air we breathe in one cycle of inspiration and expiration) and breathing frequency (Respiration Rate,RR)

As with our other muscles, our intercostals and diaphragm go through hypertrophy. This is due to the chest cavity moving more, and faster to produce our oxygen supplies. Because of this hypertrophy there is a slight increase in our chest cavity which produces more room for more gas exchange. The extra gas exchange allows for more oxygen retrieval and the removal of water and carbon dioxide. A simple eplanation of this gas exchange is: Oxygen is carried in the blood either bound to haemoglobin, or about 5% can be carried in the plasma itself. Once diffused from the cell Carbon dioxide is more complex, again only a limited supply (about 5%) can be carried in blood plasma, some may also be carried bound to haemoglobin (about 5%). The initial reaction of carbon dioxide is with water to form carbonic acid which then gets broken down into hydrogen ions and bicarbonate ions. The hydrogen ions bind with haemoglobin and the biggest portion of CO2 is removed in combination with water in the form of bicarbonate (HCO3-).

There is a decreased respiratory rate and pulmonary ventilation at rest and at submaximal exercise. Our respiration rate decreases because of a greater pulmonary efficiency and more efficient gas exchange in the alveoli. More capillaries grow around the alveoli, which increases the surface area of the alveoli (more gas exchange), and are able to pass more oxygen into the blood.

Metabolic Adaptations

The training progamme for a recreational triathlete will involve regular aerobic sessions coupled with some anaerobic strength training. This type of training places a significant metabolic demand on the body and results in many changes with regard to tissue growth, energy production and removal of wastes.

With exercise our cells, specifically muscle, gain the ability to manufacture more mitochondria. This is because of our muscles need for energy to cope with the extra demand of exercise. Mitochondria is the ‘powerhouse’ of the cell where the bulk of ATP is produced. Because of the extra mitochondria our enzyme activity increases and our production of ATP requires substrates to move through varies cycles to enable the molecules to be useable. All metabolic cycles in our body require enzymes to carry out their work, eg. Beta oxidation, glycolysis, Krebs cycle, electron transport chain. These enzymes allow or initiate chemical reactions within our cells to enable metabolism to occur.

Exercise also decreases our Respiratory Exchange Ratio (ratio of carbon dioxide released to oxygen consumed). It is where CO2 production by the working muscles becomes greater and more of the inhaled O2 gets used rather than being expelled. The respiratory exchange ratio (RER) indirectly shows the muscles oxidative capacity to get energy. This is partly due to the body using the preferred energy source of fatty acids instead of carbohydrates. Lipids/fatty acids produce around 460 molecules of ATP, so is a far superior energy source for prolonged acitivity. However, the RER increases from the ability to perform at maximum levels of exercise for longer periods of time because of high lactate tolerance.

The body’s carbohydrate metabolism is explained as the increased capacity to oxidize carbohydrate. As a result, large amounts of pyruvic acid move through the aerobic energy pathways during aerobic activity. This is in conjunction with the extra mitochondria processing more substrates and increased glycogen storage within the muscles.

Our tissues also manufacture more capillaries to cope with the hypertrophy in our heart and muscle fibres and around the alveoli for the increased volume.

So that is my version of the adaptations experienced by a recreational triathlete. Exercise will also promote feelings of wellbeing as it stimulates the sympathetic nervous system and serotonin levels. I also know from personal experience that undergoing an exercise or daily activity programme helps with my social life and enables me to meet new people where I can use and develop my social skills. I am now looking forward to my next session, I will be sure to involve other people during this or maybe just take my dogs for a run with me. Bring on those 'wellbeing' feelings I say.

This is a system more familiar to people which burns glucose quickly and coverts it to lactic acid. The result is quick ... Aerobic System (The Krebs Cycle/Citric Acid Cycle): Glucose + O2 –> CO2 + H2O + ATP This is the main ...

Glycolysis and Krebs Cycle. ANSWER: 5 is correct. QUESTION: maximum number of ATP after aerobic oxidation of a fat molecule containing three 12 carbon chains? ANSWER: Beta oxidation of fatty acid releases carbons two at a time as Acetyl ....

hormones

Produced in the anterior pituitary. Stimulated by the Hypothalamic releasing factor (GHRF). Stimulates tissue growth, mobilizes fatty acids for energy, inhibits CHO metabolism. This release is increased with exercise. Hyper causes gigantism in children and acromegly in adults.

THYROXINE

Thyrotopin is released from the hypothalamus which stimulates the release of thyroxine from the thyroid. Stimulates metabolic rate and regulates cell growth and activity. Release in increased with exercise. Hyper increased BMR, temperature, increased appetite, weight loss, hypertension, enhanced glucose, lipid and protein catabolism, loss of muscle, muscle atrophy.

Paul Andersen covers the processes of aerobic and anaerobic cellular respiration. He starts with a brief description of the two processes. He then describes ... Another good explanation of the energy transfer systems. Posted by Frith.

On Aug. 7 at 11:30 a.m., Hunter Kemper will jump into the water in the Serpentine, the famous lake in the former royal hunting ground in London now called Hyde Park, for the start of the Olympic triathlon.

Once the stored ATP is depleted (within those 10 seconds of super intense activity), the ATP can no longer be provided at the same rate and the body is forced to slow down. In other words, fatigue occurs very rapidly ...

An explanation of what this graph depicts would help all of you out for your study. Remember what we discussed about oxygen deficit at the onset of exercise, and the oxygen debt that occurs needing to be "repayed" after exercise during recovery.

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